The present invention relates generally to continuously supplying flexible raw material generally in the form of a web to a processing machine, and more particularly to a stock of ribbon material and methods for controlling twisting of the ribbon material fed to the processing machine.
Conventional processing machines, such as those used to convert narrow ribbons of raw material into finished product, run most efficiently when a continuous feed of raw material is provided. If continuous feed of raw material is not maintained, the machine must be shut down to re-thread the ribbon material. Shutting down the machine negatively impacts the efficiency of the machine, especially machines used in high volume processes such as the production of feminine care products.
Raw absorbent material used to produce feminine care products is initially manufactured as a web of absorbent material measuring one meter or more in width. The processing machine cannot process such a wide web, so the material is trimmed to form many ribbons of a more usable narrow width. The wide web is suitably scored or sheared to form the ribbons. Typically, the ribbons are then wound onto cores to form coils or xe2x80x9cpancake slitsxe2x80x9d, so-called due to the fact they resemble pancakes when laid flat. Each coil has a thickness substantially equal to a width of the ribbon material, and each successive revolution or turn of ribbon substantially overlies the preceding revolution so that the coil is no thicker than the ribbon material is wide.
The coils are shipped to a factory where the processing machine is located, and one coil at a time is mounted on a horizontal axis spindle for continuous feed of raw material into the processing machine. The machine pulls the ribbon in a direction tangential to the coil, i.e., parallel to a plane of the coil and perpendicular to an axis of the coil, so that there is no twisting of the ribbon during feeding. The spindle is a variable-speed motorized spindle with sufficient capacity for mounting only one coil of absorbent material. The spindle is variable-speed to keep tension in the ribbon as it is fed into the machine. It will be understood that at a constant linear feed rate, the coil will rotate faster as its supply of ribbon is consumed by the machine. Due to the high cost of each spindle, no more than two spindles are typically provided at the machine. Thus, as a first coil is consumed, a second coil is mounted on the second spindle, and the trailing end of the first coil is spliced to a leading end of the second coil.
An obvious disadvantage of this arrangement is that an operator must be standing by to load coils as they are consumed by the machine. The time period between changing coils (referred to as runout time) will vary with the length of the material on the coil and the speed of use by the processing machine. In the case of a relatively high throughput feminine pad machine, a typical one thousand lineal meter coil of absorbent material will be consumed in three to nine minutes. Due to this relatively short runout time, the processing machine requires constant manpower to maintain continuous feed. Moreover, the short runout time and the difficulty of loading the bulky coil on the spindle increases the likelihood that the splice will fail (e.g., due to operator error or mechanical problems in splicing) and the likelihood that the machine will have to be shutdown for re-threading.
There are other methods of providing continuous feed material to a processing machine. Rather than forming the ribbon material into narrow width coils, the ribbon material may be wound on large capacity spools. Unlike the coils described above, such spools are many times wider than the width of the ribbon, and hold significantly more material than the coils. Spools increase the runout time of the raw material but have significant disadvantages. Significant capital investment is required as compared to use of coils because most machines built to unwind one narrow coil at a time are not equipped to unwind large spools. For example, a powered turntable or xe2x80x9cunwinderxe2x80x9d is likely to be required to unwind the spool, and significantly more power will be consumed to turn the unwinder than the spindle described above. The cost of spooled raw materials is typically higher than that of coils because few raw material suppliers have spooling capability. In most cases, the material must be shipped from the point of manufacture to an external spooling vendor, which increases cost.
Another method of continuously feeding material to a processing machine is shown in U.S. Pat. No. 1,178,566 (Wright). The ribbon material is formed into a stack of coils, and an end of the upper coil is pulled parallel to the axis of the coil into the machine. This arrangement causes the ribbon material to twist as it is unwound. The patent shows a device for removing the twists including a rotatable guide which rotates in response to twists in the ribbon and a powered turntable which rotates the coils at intervals in response to rotation of the guide.
In one aspect, the present invention provides a method of preparing connected coils of wound ribbon in an alternating pattern to reduce twisting thereof during continuous axial ribbon feed to a processing machine. Each coil has a sequence of turns wound about a central axis and includes central end at an inner-most turn of the sequence of turns and an outer end at an outer-most turn of the sequence of turns. The outer end of a first coil of the coils is connected to the central end of a second coil of the coils. The method includes orienting the first coil in a clockwise winding direction and orienting the second coil in a counterclockwise winding direction such that at least some twists developed during axial ribbon feed of the first coil are removed during axial ribbon feed of the second coil.
In another aspect of the present invention, a stock of flexible ribbon material adapted for continuous feed to a processing machine includes a first coil of ribbon material having a sequence of turns wound about a central axis in a clockwise direction. The first coil includes a central end at an inner-most turn of the sequence of turns and an outer end at an outer-most turn of the sequence of turns. A second coil of ribbon material has a sequence of turns wound about a second central axis in a counterclockwise direction. The second coil includes a central end at an inner-most turn of the sequence of turns and an outer end at an outer-most turn of the sequence of turns. The outer end of the first coil is connected to the central end of the second coil.
In yet another aspect, the present invention provides a method of preparing a plurality of coils for continuous axial feed. Each coil is defined by a continuous length of coiled material having a leading end and a trailing end. The method includes receiving the coils, exposing the trailing end of the coils, splicing the trailing end of each coil to the leading end of an adjacent coil, and orienting the coils so that when twists develop during axial feed of one of said coils at least some of the twists are removed during axial feed of a subsequent one of said coils.
In still another aspect, the present invention provides a method of preparing a plurality of coils including receiving the coils, exposing the trailing end of the coils, splicing the trailing end of each coil to the leading end of an adjacent coil, shipping the coils to a processing machine, and axially feeding the plurality of coils into the processing machine.
Other features of the present invention will be in part apparent and in part pointed out hereinafter.